Radar based safety systems for automobiles require directional antennas capable of distinguishing targets in a wide field of view in front of vehicles. It has been found advantageous to provide such safety systems with both short and long range radar coverage, where the antenna requirements differ for each type of radar coverage. For long range radar coverage extending from about −7.5° to about 7.5° in azimuth in front of a vehicle, radar antenna beamwidths of about 3° to 4° have been found effective for radiation beams in this angular area of coverage. For short range radar coverage extending from about −80° to 80° in azimuth (except for the coverage area of the long range radar), radar antenna beamwidths of about 10° have been found effective for radiation beams within this angular area of coverage.
In the past, up to five separate antenna structures with different apertures have been required to provide the necessary radiation beams within the individual areas of angular coverage for both a long range radar operating at 77 GHz, and a short range radar operating at 24 GHz. These separate antennas take up a significant amount of space on a vehicle, and can be relatively expensive as compared to other radar system components.
Accordingly, there exists a need for an inexpensive, integrated multi-beam antenna that can provide multiple radiation beams within specified areas of angular coverage for both short and long range radars in automotive radar safety systems.